The fixtures file in the control repo checks out shared_hieradata into the root of the control repo, while deptool attempts to create a symlink into the deptool cache:
bundler: failed to load command: check_dependencies (/home/nick/.pdk/cache/ruby/2.5.0/bin/check_dependencies)
Errno::EEXIST: File exists @ syserr_fail2_in - /home/nick/git/puppet/persistent_systems_control/shared_hieradata
/opt/puppetlabs/pdk/private/ruby/2.5.9/lib/ruby/2.5.0/fileutils.rb:323:in `symlink'
/opt/puppetlabs/pdk/private/ruby/2.5.9/lib/ruby/2.5.0/fileutils.rb:323:in `block in ln_s'
/opt/puppetlabs/pdk/private/ruby/2.5.9/lib/ruby/2.5.0/fileutils.rb:1477:in `fu_each_src_dest0'
/opt/puppetlabs/pdk/private/ruby/2.5.9/lib/ruby/2.5.0/fileutils.rb:321:in `ln_s'
/home/nick/git/puppet/puppet-deptool/lib/puppet-deptool/environment.rb:100:in `block in prepare_envlink_targets'
/home/nick/git/puppet/puppet-deptool/lib/puppet-deptool/environment.rb:90:in `each'
/home/nick/git/puppet/puppet-deptool/lib/puppet-deptool/environment.rb:90:in `prepare_envlink_targets'
/home/nick/git/puppet/puppet-deptool/lib/puppet-deptool/environment.rb:64:in `deploy'
/home/nick/git/puppet/puppet-deptool/lib/puppet-deptool/parser.rb:156:in `deploy_environment'
/home/nick/git/puppet/puppet-deptool/bin/check_dependencies:8:in `<top (required)>'
/home/nick/.pdk/cache/ruby/2.5.0/bin/check_dependencies:23:in `load'
/home/nick/.pdk/cache/ruby/2.5.0/bin/check_dependencies:23:in `<top (required)>'
The fixtures file in the control repo checks out shared_hieradata into the root of the control repo, while deptool attempts to create a symlink into the deptool cache: